In recent years, there has been a trend seen in that silicon wafers having a larger diameter are used for semiconductor manufacturing. For this reason, when semiconductor manufacturing apparatuses are used, it has become necessary to supply a treatment gas to a chamber through a plurality of supply lines, and to precisely control a flow rate ratio of the gas passing through these supply lines.
FIG. 7 illustrates one example of a gas supply system with which gas is supplied to a chamber through a plurality of supply lines for a conventional semiconductor manufacturing apparatus, wherein flow rate control systems FCS1, FCS2 are provided with gas supply lines GL1, GL2, respectively, thus allowing regulation of the flow rate ratio γ=Q1/Q2 of the supply lines GL1, GL2. In FIG. 7, ST designates a gas supply line, G designates a treatment gas, C designates a chamber, D designates a gas discharger, H designates a wafer, and I designates a wafer holding base. However, with the apparatus as shown in FIG. 7, two flow rate control system units FCS1, FCS2 are required, which upsizes the semiconductor manufacturing apparatus and raises costs for equipment and maintenance, thus making it difficult to downsize equipment and to reduce costs.
FIG. 8 shows gas supply equipment previously developed by the inventor of the present invention in order to improve the aforementioned shortcomings of the equipment shown in FIG. 7, wherein gas G is controlled to have a flow rate Q set by the flow rate control system FCS so that gas G is supplied to a chamber C with a desired flow rate ratio γ=Q1/Q2 through supply lines GL1, GL2, which are provided with pressure type diverted flow rate controllers FV1, FV2 controlled by a diverted flow rate control apparatus FRC.
In particular, the gas supply apparatus shown in FIG. 8 is provided with a gas discharger D, which is equipped with orifices OL1, OL2 having specific diameters φ1, φ2, respectively, installed inside the chamber C. The gas supply apparatus of FIG. 8 is made so that gas of a total quantity Q=Q1+Q2 is supplied into the chamber C with desired diverted flow rates Q1 and Q2, expressed by Q1=K1P3′ and Q2=K2P3″ (where K1 and K2 are constants determined by the cross sectional areas, and the like, of orifices OL1, OL2), passing through the orifices OL1, OL2, respectively, of the gas discharger D by regulating the gas pressure P3′, P3″ on the downstream side by using the diverted flow rate controllers FV1, FV2. (Japanese Unexamined Patent Application Publication No. 2004-5308)
However, with the gas supply apparatus shown in FIG. 8, there remains a problem in that the shape, and the like, of the gas discharger D are subsequently restricted because the gas supply apparatus includes that gas discharger D, equipped with orifices OL1, OL2 having specified diameters φ1, φ2, installed inside the chamber C. Because two flow rate control system units FCS1, FCS2 are not needed by the apparatus shown in FIG. 8, compared with the aforementioned gas supply apparatus shown in FIG. 7, costs for equipment, and the like, can be reduced in comparison with the aforementioned gas supply apparatus of FIG. 7. However, it is disadvantageous in that the gas supply apparatus of FIG. 8 requires two diverted flow rate controller units FV1, FV2, and also a diverted flow control apparatus FRC. This fact doesn't allow installation costs to be substantially reduced and it doesn't allow drastic downsizing of the diverted gas supply apparatus. In addition, another disadvantage is that it becomes too complicated to control of the flow rate ratio Q1/Q2.
Furthermore, FIG. 9 illustrates another system that has been developed previously by the inventors of the present invention to overcome the aforementioned shortcomings of the gas supply system shown in FIG. 8 (Japanese Unexamined Patent Application Publication No. 2004-5308). The gas supply system of FIG. 9 is constituted so that by using simply structured open/close valves V1, V2, a pressure type diverted flow rate controller SV, and a flow rate ratio control apparatus CT, the total flow rate Q=Q1+Q2 of the gas flow G is supplied into the chamber C with a desired diverted flow rate ratio γ=Q1/Q2 in such a manner that the open/close valve of the supply line with a larger flow rate is fully opened and the degree of opening of a pressure type diverted flow rate controller SV is regulated, so as to conduct pressure adjustment of both diverted supply lines GL1, GL2 by regulating gas flow rate from a supply line on the larger flow rate side to a supply line on the smaller flow rate side. (Japanese Unexamined Patent Application Publication No. 2005-11258)
However, the same disadvantages with the aforementioned gas supply apparatus shown in FIG. 8 (Japanese Unexamined Patent Application Publication No. 2004-5308) remain unsolved even with the gas supply apparatus of FIG. 9, so it has not been possible to substantially downsize the gas supply apparatus and to reduce equipment costs drastically, and also it has not been possible to freely choose the form of the gas discharger D without limitation.
As shown in FIG. 10, flow rate control systems (Japanese Unexamined Patent Application Publication No. 2003-323217 and others) have been developed as a kind of flow diverting gas supply apparatus, wherein branch supply passages GL1, GL2 are equipped with sonic velocity nozzles SN1, SN2, respectively, and the pressure P1 on the upstream side pipe passage from the sonic velocity nozzles SN1, SN2 is regulated using an automatic pressure controller ACP, thus allowing gas supply quantities Q1, Q2 from the branch supply passages GL1, GL2 to be regulated. In FIG. 10, ACQ designates a flow rate control part, and V1, V2 designate control valves.
An object of the flow diverting supply apparatus is to simultaneously control gas flow rates Q1, Q2 passing through sonic velocity nozzles SN1, SN2 (or orifices) in a manner such that the primary side pressure P1 is regulated using an automatic pressure controller ACP. It is not an immediate object of the invention to regulate the flow rate ratio γ=Q1/Q2 of the branch pipe passages GL1, GL2 at any given ratio.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-5308    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2005-11258    Patent Document 3: Japanese Unexamined Patent Application Publication No. 2003-323217